Towards a taxonomy of conjugative plasmids

•Conjugative plasmids are key mediators of Horizontal Gene Transfer in Bacteria, frequently mediating environmental adaptation.•In order to make sense of the increasingly amount of plasmid genomic data, there is a need of appropriate, functional ways to classify conjugative plasmids.•Conjugative plasmids form distinguishable clades and phylogenies, thus they are not refractory to taxonomic classification.•Translating criteria employed in bacterial taxonomy might be enough to provide an operational taxonomy for conjugative plasmids.

Conjugative plasmids are the keystone of horizontal gene transfer. Metagenomic research and clinical understanding of plasmid transmission beg for a taxonomical approach to conjugative plasmid classification. Up to now, a meaningful classification was difficult to achieve for lack of appropriate analytical tools. The advent of the genomic era revolutionized the landscape, offering a plethora of plasmid sequences as well as bioinformatic analytical tools. Given the need and the opportunity, in view of the available evidence, a taxonomy of conjugative plasmids is proposed in the hope that it will leverage plasmid studies.